Control mechanism for hoists, lifts, and the like



H. W. C. LIDDIARD CONTROL MECHANISM i 03 uols'rs, L'IF'IS, AND THE LIKEFiled latch 31. 1926 '3 Sheets-Sheet 1 1nvfitOP Hugh WC, LLddLaPd D HMAL-7% Hus Attom e9 Oct. 16, 1928.

H. w; QUDDIARD CONTROL MECHANISM FOR HOISTS, LIFTS, AND THE LIKE FiledMarch 31. 1926 5 Sheets-Sheet 2 Hus Attorney.

H. W. C. LIDDIARD I CONTROL MECHANISM FOR HOIS'I'S, LIFTS, AND THE LIKEFiled larch 51, 1926 v s Sheets-Sheet 5 Fig, 4.

Inventor Hugh w. c. Liddiard,

Hs Attorney.

Patented bet; l6,

UNITED STATES PATENT OFFICE.

HUGH W. C. LIDDI'ABD, OF RUGBY, ENGLAND, A SSIGNOR TO GENERAL ELECTRIC 1COMPANY, A CORPORATION OF NEW YORK.

ooN'rBoL mncnnmsu ron norsrs, Lm'rs, AND rim LIKE.

Application filed March 31, 1936, Serial No. 98,875, and in GreatBritainApril 6, 1925.

In an electrically-operated hoist, or lift, dilficulty is oftenexperienced when using automatic control in ensuring that the skip,

or cage, is brought to the correct level under all conditions of load.It is usual to bring 1n some :torm of slowing mechanlsm at a point somedistance from the end of the travel, and

to stop the skip or cage by a final limit switch. lhe ordinary form ofhoist is one in which the skip or cage is counter-weighted so that thestopping distance depends on the unbalanced load, the inertia, and thespeed of travel, and unless special arrangements are provided it isfound difiicult to ensure that the skip or cage is reduced to a.sufficiently low speed with light loads, ascending, and, at the sametime avoid stalling with heavy loads,

ascending, before reaching the final stop switch, and it is necessary toutilize some form of discriminatingdevice to bring in various degrees ofbraking on the operation of the slow limit switch, in order to ensurethat on the one hand the skip shall be sufiiciently reduced in speed,and on the other that it shall not stop. In descending, the condition isthe opposite, since with a light load in the skip the unbalanced load ismoving upward, and with a heavy load in the skip the unbalancedload ismoving downward.

The present invention applies particularly to electricallydriven hoistsor lifts, in which the acceleration of the hoist or lift is carried outautomatically by means of contactor gear or the like, under currentlimit control. The time taken to accelerate up to full speed andlikewise the distance travelledduring the acceleration is dependent onthe same factors as govern the amount of braking required to bring thelift or hoist to the required reduced speed prior to being finallystopped. ll propose to use the distance covered during this acceleratingperiod for the purposes of seecting the amount of hralring required todsthe end of trip, since this distance sled talres into account thevariable factors of the value the direction of movement of theunhalanced load.

the accompanying drawings, Figure i represents diagrammatically aninclined hoist in Whichthe skip S is hoisted up an incline; at the topof the incline is a stop limit switch 6 which is tripped by the ski atthe position corresponding to the require stopping position. atrepresents the slow limit switch mentioned above, introducing a variedamount of braking, according to the requirements as determined by theposition of the skip, relative to the selector switches a, b, c at theend of the accelerating period. Similar arrangesents the armature of thedriving motor. 1, 2,

3 and 4 represent the reversing contactors, contactors 1 and 3 beingclosed for one direction, and 2 and 4 for the reverse direction.Contactors 5, 6, 7, 8, 9 and 10 are the ordinary accelerating contactorsfor bringing the motor up to speed, these being under current limitcontrol, and cuttin out the starting resistance of R in the ordinarymanner.

R, is a diverter resistance which is introduced during the slowingperiod for reducing the speed as mentioned above, this diverterresistance being introduced by contactor D, and the amount of which isvaried according to the closing of contactors A, B and C, thus varyingthe amount of braking efi'ect according to the requirements. F.represents the brake magnet contactor. a

Figure 3 shows a suitable arrangement of the control circuits for theabove, in which contactor coils are numbered and lettered so as tocorrespond to the numbers and letters on erating contactors in the knownmanner.

When all the contactors 5, 6, 7, 8, 9 and 3.0 are closed, the motor isup to approximately full or normal speed,'and on 10 closing, aninterlock completes the circuit to the diverter selecting contactors A,B and C, this circuit being completed through one of the switches a band 0 1f reversing. contactors 1 and 3 are c osed, and through switchesa,, 6,, c, it reversing contactors 2 and 4 are closed, selec: tionbetween these two circuits being accomplished by suitable interlocks onthe reversing contactors. Should the skip not have reached switcha (Sorthe corresponding switch a, if going in a ownward direction), when thelast accelerating contactor is closed then the diverter selectingcontactor A will close and be retained through its own interlocks.Should the skip have passed the switch a (or the corresponding switch inthe downward direction a,), but not have reached switch I) (or thecorresponding switch 6,), then diverter. selectin contactor B will beclosed and retained t rough its own interlocks. Similarly, if the skiphas passed switch I) and not reached 0, then diverter contactor C willbe closed, and finall if it passes all three sfvitches none of t ediverter contactors will 0 ose.

On the skip reaching the slow limit switch 11 (or corresponding switchd,), this slow switch opens the accelerating contactors 5 to 10, whichputs full starting-resistances in series with the motor and closesdiverter contactor D, which puts an appropriate amount of the diverterresistance R, across the motor armature accordin to thediverterselecting contactor closed. e forward and reverse sto limit switches areindicated at e and e.

s before stated, the system of Fig. 4 incorporates the system of Fig. 2and the system of Fig. 3, in accordance with the invention. In thisfigure, the various parts of the system are lettered and numbered thesame as the corresponding parts of Figs. 2 and 3 and the operation ofthis system is the same as ski .ings4'an that which has been vein inconnection with Fig. 3. The field wmding of the motor has been omittedas in Fig. 2,'since this winding is presumed. Thus, with the ski at theplace on the incline as indicated at t e top of 1g. 4, assuming that itis desired that the proceed up the incline, the master switch P willbethrown to the right, thereb completin a circuit for the operating win1' of contactors 4 and 1, respectively through a circuit which includesthe right-hand segments of the master switch, the coils 4' an 1', limitswitch 0, to the other supply conductor. This will efiect the closing ofthe contactors 1 and 4 and a circuit for the armature M of the motorwill be completed throu h the contactor 4, resistor R,, armature of t cmotor,contacts of contactor 1 to the other supply conductor. Upon theclosing'of contactor 1, the lower interlock or auxil ary switch 1,thereof establishes an energizing circuit for the winding of theelectromagnetic brake F, this cirout being readily traced. The contactor1 in closirg likewise establishes an energizing circuit or contactor 5through the auxiliary switch 1 the travel limit switch d and the on theacceleration of the motor. However, the current limit auxiliary switch5, is placed under a bias to the closed position. It will be rememberedthat I have stated that my invention is particularly adapted to a systemin which the motor is accelerated under current limit control. I haveselected a conventional system for. illustrating this currentlimitcontroland I would have it understood that the particular method ofcurrent limit control which have selected for purposes of illustratingthe principles of the invention is not necessary to carrying theinvention into effect, since other well known forms of can rent limitcontrol may be utilized as desired.

The auxiliary switch 5, is magnetically held in the open position untilthe current taken by the motor has dro pedto a predetermined value. Whenthis happens the auxiliary switch will close its contacts, therebycompleting an energizing circuit for the winding 6' of contactor 6.Oontacto'r' 6 is thus closed and the auxiliary switch 6, is likewiselaced under a bias to the closed position. en 'the motor armaturecurrent again drops to the predetermined value, the auxiliary switch 6,will close its contacts and establish the energizing circuit for thewinding 7' of contactor 7. The contactors 8, 9 and 10are thenautomatically closed in. succession under current limit control by theclosing of the auxiliary switch 7,to energize the operatin winding 8 ofcontactor 8, the closing 0 auxiliary switch 8, under current limitcontrol to establish the energizin circuit for the winding 9 ofcontactor 9 an the closing of the auxiliary switch 9, under currentlimit control to establish the ener-' gizin circuit for the winding 10'of contactor 10. s explained in connection with Fi 2, thesecontactorssuccessively shunt sectlons of the resistor R, to effect theacceleration of the motor to the normal running speed.

It will' be observed that the auxiliary switches associated with thecontactor 10 establish control circuits whereby the contactors A, B andC may be subsequently selectively closed. Thus, in case the contactor 10has closed before the skip reaches the se- 1 lector switch a to operatethe same, the windand A. of A will be energized through a circuit whichmay be traced as follows i Through the auxiliary switch 1, associatedwith conmotor 1, auxiliary switch 10,, selector switch a, coil A ofcontactor A, through the auxil:

'iary switch B, associated with contactor B when the contactorv D isclosed, merely a small portion of resistor R will be included about thearmature M of the motor, and a' plomparatively great braking effect willlb The winding circuit for the coil of contactor A is carried through anauxiliary switch associated with contactor B and also an auxiliaryswitch associated with contactor C so as to prevent the closing ofcontactor A in case either the contactors B or C are closed. Likewise,the coil circuit for contactor B is carried through auxiliary switchesC, and A associated respectively with contactors G and A and the coilcircuit for contactor C is carried through an auxiliary switch Bassociated with contactor B and another auxiliary switch A, associatedwith contactor A, for a similar purpose. In other words, it is desiredthat merely one of these diverter resistor contactors be closed at atime so that a definite value of the armature shunting resistance is hadin dependence upon the extent of the travel of the skip during theacceleration interval while the motor is being accelerated under currentlimit control.

If instead of the contactor 10 closing before the skip had reached theselector switch a, the contactor 10. had closed when the skip wasbetween selector switches a and Z), contactor A would not have closedbecause of the fact that the closing of this latter contactor isdependent upon the prior closing of contactor 10. Thus, in this case acircuit will be completed for the winding B of contactor B through acircuit which may be traced as follows: From the left-hand conductor ofthe supply circuit through auxiliary switch 1,, of

contactor 1, auxiliary switch 10, of contactor 10, selector switch a inthe right-hand position thereof, selector switch 6 in the positionindicated in the drawing, coil B of contactor B, auxiliary switch C, ofcontactor C, auxiliary switch A of contactor A to the right-handcontactor of the source of supply. In case the skip or car had beenloaded such that the car had proceeded past the selector switch 6 beforethe final resistor contactor 10 had closed, and before the car hadreached the track selector switch 0, the contactor C would be closed,the circuit for the windin C of this contactor being as follows Througthe auxiliary switch 1, of contactor 1, auxiliary switch 10, ofcontactor 10, track selector switch I) in the right-hand positionthereof, track selector switches c and a, coil 0 and auxiliary switchesB and A, associated with contactors B and A, respectively, to the othersupply conductor. A braking eifect correspondingto the unbalanced loadwould thus be secured at the limit of travel.

In case the acceleration of the motor had been such that the car hadproceeded past the selector switch a before the final resistorcontactor-10 had closed, neither of the diverter resistor contactors A,B or-C would be closed. In any event, when the car reaches the selectorswitch 03, the winding of contactor D is energized through a circuitwhich may be traced as follows: Through the auxiliary switch 1,,,associated with contactor 1, selector switchrl inthe right-hand positionthere- 'of, coil of contactor D to the other supply conductor. Theoperation of the selector switch 03 from its left-hand or lower to itsright-hand or upper position, effects the deenergization of the winding5' of contactor 5 so that contactors 5, 6,7, 8 and 9 will successivelyopen, thereby reinserting the resistor R, in the motor armature circuit.

In case any of the diverter resistor contactors A, B and C had beenpreviously closed as above explained, the contactor would have remainedclosed, since although the winding circuit for these contactors isthrough an auxiliary switch associated with contactor 10, each of thesecontactors in closing establishes a maintaining circuit for itselfthrough an auxiliary switch associated with contactor 1. Thus, whencontactor A closes it establishes a maintaining circuit for itself whichmay be traced as follows: Through the auxiliary switch 1,,, auxiliaryswitch A, of contactor A, auxiliary switch 13,, auxiliary switch C tothe other supply conductor- Had the contactor B been closed, it wouldestablish a maintaining circuit for the coil thereof through itsauxiliary switch and had contactor C been closed, it would haveestablished a maintaining circuit for its coil through its auxiliaryswitch 0,. That means that the particular one of contactors A, B or Cwhich had been closed would have remained closed until the linecontactor 1 is opened. The line contactor 1 is deenergized and openedwhen the final limit switch 6 is opened. When this happens, the variouscontactors are caused to return to their positions indicated in thedrawing.

From the explanation which has been given in connection with theoperation of the equipment, while the skip is proceeding up the incline,it is believed that those skilled in the art will readily understand theoperation of the -equipment when the skip is proceeding down theincline. To initiate the downward movement, the master switch P isthrown to its lefthand position. The windings 2 and 3 of contactors 2and 3 will in this case be closed so as to connect the motor armature tothe source of supply for the reverse direction of operation. In thiscase-the auxiliary switch 2, performs a similar function to theauxiliary switch 1, associated contactor l in effecting the release oftheelectromagnetic brake F, the auxiliary switches 2,, and auxiliaryswitch 2,,, associated with contactor 2 perform similar functions tothose described in connection with auxiliary switches 1 and 1respectively, of contactor 1. In this in dependence on the extent oftravel of the thelauxiliary switch 10 performs a similar furiction tothe described function of auxiliary switch 10 and the'auxiliary switchesA B and C perform similar functions to those those described inconnection with auxiliary switches-A B,.and 0,, respectively. Likewisein this case the selector switches a, b, c, d and e perform similarfunctions to those described in connection with track selectorswitches'a, b, a, d and a respectively. It is thought that a detaileddescription of the operation of the equipment when the skip isproceeding in the downward direction wi 1 be unnecessary, since thoseskilled in the art will readily understand the same from a considerationof the operation of the equipment when the skip is proceeding in the updirection.

Although a articular arrangement of con-- trol from a direct current suply using diverter control for braking is shown, the invention is notlimited tov this arrangement, but is equally applicable where analternating current supply 1s utilized provided the required selectivebraking effect can be-introuced accordin to-the position of the skip atthe end of the accelerating period. It is also to be noted that anynumber of diverter selecting switches and corresponding diverterselecting contactors can he used, according to the requirements, withoutdeparting from the spirit of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of controlling a motor driven device which consists inapplying an acceleration effect to the device to effect accelerationthereof to substantially the normal running speed, continuing therunning of the device at substantially said speed, and then before alimit of operation of-the device is reached applying to the device abraking effect which is automatically varied in value 'in depen devicedurin the accelerating period.

2. In com ination, a device, a motor for driving the same, accelerationcontrolling means for said motor set in operation before a limit oftravel of the device is reached for applying a braking effect to thedevice, and means for automaticall varying the braking efi'ect ap liedby said rst mentioned means deuce on the extent of travel of said deviceduring 7 the period in which the device is' accelerate to the normalrunning speed.

3. In a hoist or the like, a skip or cage, an

electric motor for operatin the same, acceleration cont-rolling means%or said motor, a resistor for effecting retardation of themotor speed,means set in operation before a limit of operation of said ski or cageis reached for connecting the sai resistor with said motor, and meansfor automatically varying the retardation effect of said resistor in dependence on the extent of travel of said skip or cage duringtheacceleration thereof to substantially a normal running speed.

4. In a hoist or the like, a skip or cage, an electric motor foroperating the same, means for effecting acceleration of said motor to anormal running speed, a diverter resistor for the armature of said motorfor efiecting'retardation of themotor speed, a plurality of switches forshuntin sections of said resistor, a limit switch for e ecting theconnection of said resistor to the armature of said motor before a.limit of o ration ofsaid skip or cage is reached, an a plurality ofselector switches for selectively controllin the closing of saidshunting switches in ependence on the extent of travel of said skip orcage 7 during 'theacceleration thereof to substantially normal runningspeed.

- In witness whereof, I have hereunto set my handthis 16th day of March,1926.

. HUGH w. GLIDDIARD.

